Partial trisomy of the long arm of chromosome 1: prenatal diagnosis, clinical evaluation and cytogenetic findings. Case report and review of the literature.

Partial trisomy of the long arm of chromosome 1 is a relatively rare cytogenetic anomaly. Its phenotype has still not been completely defined, because of the cytogenetic heterogeneity of the cases so far described. We report a prenatal case of partial 1q trisomy associated with partial monosomy 4q, secondary to balanced maternal translocation t(1;4). The trisomic segment extended from 1q31.1 to qter and the monosomy 4q was from 4q35.2 to qter. The phenotypic anomalies found by post-mortem and autopsy examinations were compared with those of similar cases reported in the literature. We performed standard cytogenetics and fluorescence in situ hybridization. Cerebral ventriculomegaly, present in our case, seemed to be a constant feature in partial 1q trisomies, so this cerebral malformation could be considered as the main echographic marker for this chromosomal imbalance and trisomy 1q should be added to the list of chromosomal abnormalities associated with ventriculomegaly.

Patau syndrome with long survival in a case of unusual mosaic trisomy 13.

We report a 12-year-old patient with Patau syndrome, in whom two cell lines were present from birth, one with total trisomy 13 due to isochromosome (13q), and one with partial trisomy 13. A cytogenetic re-evaluation at 9 years of age brought to light in skin fibroblasts a third cell line, partially monosomic for chromosome 13. The derivatives (13) present in the three cell lines were characterized through fluorescence in situ hybridization (FISH) experiments with suitable probes; the results suggested a sequence of rearrangements which beginning from an isochromosome (13q) could have led to the other two derivatives. We report the clinical data at birth and at the age of 12; at this age pigmentary lesions with phylloid pattern were noted. Cytogenetic findings of the chromosomal analyses on different tissues, including skin fibroblasts from differently pigmented areas, are also reported.